﻿using System;
using System.Collections.Generic;
using System.DrawingCore;
using System.DrawingCore.Imaging;
using System.IO;
using System.Linq;
using System.Threading.Tasks;

namespace TestJ.Tool
{
    /// <summary>
    /// 验证码
    /// </summary>
    public class VerificationCodeService
    {
        /// <summary>
        /// 该方法用于生成指定位数的随机数
        /// </summary>
        /// <param name="verificationCodeNum">参数是随机数的位数</param>
        /// <returns>返回一个随机数字符串</returns>
        private static string RndNum(int verificationCodeNum)
        {
            //验证码可以显示的字符集合
            string Vchar = "0,1,2,3,4,5,6,7,8,9,a,b,c,d,e,f,g,h,i,j,k,l,m,n,p" +
                ",q,r,s,t,u,v,w,x,y,z,A,B,C,D,E,F,G,H,I,J,K,L,M,N,P,P,Q" +
                ",R,S,T,U,V,W,X,Y,Z";
            string[] VcArray = Vchar.Split(new char[] { ',' });//拆分成数组
            string code = "";//产生的随机数
            int temp = -1;//记录上次随机数值，尽量避避免生产几个一样的随机数

            Random rand = new Random();
            //采用一个简单的算法以保证生成随机数的不同
            for (int i = 1; i < verificationCodeNum + 1; i++)
            {
                if (temp != -1)
                {
                    rand = new Random(i * temp * unchecked((int)DateTime.Now.Ticks));//初始化随机类
                }
                int t = rand.Next(61);//获取随机数
                if (temp != -1 && temp == t)
                {
                    return RndNum(verificationCodeNum);//如果获取的随机数重复，则递归调用
                }
                temp = t;//把本次产生的随机数记录起来
                code += VcArray[t];//随机数的位数加一
            }
            return code;
        }

        /// <summary>
        /// 该方法是将生成的随机数写入图像文件
        /// </summary>
        /// <param name="code">code是一个随机数</param>
        /// <param name="numbers">生成位数（默认4位）</param>
        public static MemoryStream Create(out string code, int numbers = 4)
        {
            code = RndNum(numbers);
            Bitmap Img = null;
            Graphics g = null;
            MemoryStream ms = null;
            try
            {
                Random random = new Random();

                //验证码颜色集合
                Color[] c = { Color.Black, Color.Red, Color.DarkBlue, Color.Green, Color.Orange, Color.Brown, Color.DarkCyan, Color.Purple };

                //验证码字体集合
                string[] fonts = { "Verdana", "Microsoft Sans Serif", "Comic Sans MS", "Arial", "宋体" };

                //定义图像的大小，生成图像的实例
                Img = new Bitmap(code.Length * 18, 32);

                g = Graphics.FromImage(Img);//从Img对象生成新的Graphics对象

                g.Clear(Color.White);//背景设为白色

                //在随机位置画背景点
                for (int i = 0; i < 100; i++)
                {
                    int x = random.Next(Img.Width);
                    int y = random.Next(Img.Height);
                    g.DrawRectangle(new Pen(Color.LightGray, 0), x, y, 1, 1);
                }
                //验证码绘制在g中
                for (int i = 0; i < code.Length; i++)
                {
                    int cindex = random.Next(7);//随机颜色索引值
                    int findex = random.Next(5);//随机字体索引值
                    Font f = new Font(fonts[findex], 15, FontStyle.Bold);//字体
                    Brush b = new SolidBrush(c[cindex]);//颜色
                    int ii = 4;
                    if ((i + 1) % 2 == 0)//控制验证码不在同一高度
                    {
                        ii = 2;
                    }
                    g.DrawString(code.Substring(i, 1), f, b, 3 + (i * 12), ii);//绘制一个验证字符
                }
                ms = new MemoryStream();//生成内存流对象
                Img.Save(ms, ImageFormat.Png);//将此图像以Png图像文件的格式保存到流中
                //回收资源
                g.Dispose();
                Img.Dispose();
                return ms;
            }
            catch (Exception e)
            {

                throw new Exception($"{e.Message},{e.StackTrace}");
            }
            finally
            {

            }

        }
    }
}
